Traditional approaches to estimate length at first maturity (L50 ) retrieve better results than alternative ones in a Neotropical heptapterid

Length at first maturity (L₅₀ ) is an important tool for the management and conservation of fish populations. Traditional approaches based on macroscopic and microscopic maturity staging exhibit high accuracy and precision, while alternative approaches (e.g., I_g -based staging, stanza changing point) are less resource-demanding. Herein, we compare four approaches to estimate L₅₀ in a population of the heptapterid Rhamdioglanis transfasciatus from Atlantic Forest streams. Fish were sampled monthly during a year by using electrofishing. We measured the length (cm), mass (g), and gonad mass (g) of each specimen, then classified their maturity status macroscopically and microscopically. Alternative approaches were strongly discordant from traditional ones. Logistic curves considering mature individuals as those displaying at least 1% of the maximum I_g in the sample greatly underestimated L₅₀ for females and overestimated L₅₀ for males. The stanza changing point derived from the polyphasic growth model underestimated L₅₀ in both cases. Despite the increasing development of less onerous approaches, it seems that they are not suitable for all fish populations and the requirements to use such approaches demand further investigation.

Structure-activity relationships and mechanism of action of tetragomycin derivatives as inhibitors of Staphylococcus aureus staphyloxanthin biosynthesis

Despite the main strategy to overcome bacterial resistance has focused on the development of more potent antimicrobial agents, the evolutionary pressure caused by such drugs makes this strategy limited. Molecules that interfere with virulence factors appear as a promising alternative though, as they cause reduced selective pressure. As a matter of fact, staphyloxanthin biosynthesis inhibition (STXBI) has been pursued as promising strategy to reduce S. aureus virulence. Herein, we report the inhibitory profile of 27 tetrangomycin derivatives over staphyloxanthin production. The experimental result showed that naphthoquinone dehydro-α-lapachone (25 - EC₅₀ = 57.29 ± 1.15 μM) and 2-Isopropylnaphtho[2,3-b]furan-4,9-dione (26 EC₅₀ = 82.10 ± 1.09 μM) are the most potent compounds and suggest that hydrogen acceptor groups and lipophilic moieties decorating the naphthoquinone ring are crucial for STXBI. In addition, we present an in situ analysis, through RAMAN spectroscopy, that is inexpensive and might be employed to probe the mechanism of action of staphyloxanthin biosynthesis inhibitors. Therefore, our molecular simplification strategies afforded promising lead compounds for the development of drugs that modulate S. aureus staphyloxanthin biosynthesis.

Essential oil from Zanthoxylum tingoassuiba loaded into multilamellar liposomes useful as antimicrobial agents

Zanthoxylum tingoassuiba essential oil (EO) is a complex mixture of organic compounds among which methyl-N-methylanthranilate and sesquiterpene alcohol alpha-bisabolol represent the main compounds. The essential oil antimicrobial activity was studied against bacteria and fungi cells by diffusion disk method and significant activity was observed against S. aureus, S. aureus isolated multi-resistant and the dermathophyte fungi. Essential oil from Zanthoxylum tingoassuiba loaded into DPPC multilamellar liposomes (MLV) was successfully produced through a thin film hydration method with mean diameter of 9.37 +/- 4.69 microm. The EO-loaded liposomes showed adequate sphericity and narrower size distribution than empty liposomes. Results also showed that Zanthoxylum tingoassuiba essential oil can be incorporated in appreciable amounts (43.7 +/- 6.0%) in the prepared vesicular dispersions. A strong interaction between essential oil and lipid bilayer was indicated by a significant decrease in T(m) of the EO-loaded liposomes related to empty vesicles. Essential oil showed incomplete release profile from liposomes, suggesting that EO-loaded liposomes will be useful in pharmaceutical applications to enhance essential oil targeting to cells.

Cloning and characterization of a LON gene homologue from the human pathogen Paracoccidioides brasiliensis

A LON gene homologue from the human pathogen Paracoccidioides brasiliensis (PbLON) has been cloned, sequenced and characterized. It encodes a putative ATP-dependent proteinase Lon, which in Saccharomyces cerevisisae (PIM1) is a heat-inducible protein involved in the degradation of abnormal or short-lived proteins in the mitochondria. The PbLON ORF is within a 3369 bp fragment interrupted by two introns located in the 3'segment. The 5' and 3' regions flanking the ORF contain sequences which resemble known transcription elements. Several transcription binding factor motifs have also been found, including sites for heat shock/stress response and nitrogen control. The deduced protein consists of 1063 residues containing a mitochondrial import signal at the N-terminus and conserved ATP-binding (GPPGVGKT) and serine catalytic (KDGPSAG) sites. It shares high identity with Lon homologues from S. cerevisiae (73%), Homo sapiens (62%) and Escherichia coli (56%). In P. brasiliensis, an MDJ1 putative gene has also been partially sequenced adjacent to PbLON, possibly sharing divergently orientated promoter elements. This chromosomal organization is interesting, since Mdj1p is a heat shock chaperone essential for substrate degradation by PIM1 in yeast.

Fungal morphogenesis and virulence

Phenotypic variability in pathogenic fungi has long been correlated with virulence, but specific genetic and molecular mechanisms are only recently being unraveled. Fungal morphogenesis, reflecting the expression of several regulated genes, and the capacity of the rising forms or phases to cause disease has been focused on at the XIVth Congress of the International Society for Human and Animal Mycology. Three experimental models of pathogenic fungi have been discussed. In Cryptococcus neoformans, phenotypic variability or switching represents controlled and programmed changes rather than random mutations. Evaluated phenotypic traits were the capsular polysaccharide, cell and colony morphology and virulence. In the dimorphic Paracoccidioides brasiliensis, the serine-thiol proteinase from the yeast phase cleaves the main components of the basal membrane, thus being potentially relevant in fungal dissemination. In Candida albicans, relationships between adhesion proteins and those of lymphocytes and neutrophils are related to fungal pathogenicity. Regulation of the directional growth of hyphae and its tropic responses are correlated with the invasive potential of C. albicans.

Polymorphism in the gene coding for the immunodominant antigen gp43 from the pathogenic fungus Paracoccidioides brasiliensis

The gp43 glycoprotein is an immune-dominant antigen in patients with paracoccidioidomycosis (PCM). It is protective against murine PCM and is a putative virulence factor. The gp43 gene of Paracoccidioides brasiliensis B-339 is located in a 1,329-bp DNA fragment that includes two exons, a 78-bp intron, and a leader peptide-coding region of 105 bp. Polymorphism in gp43 has been suggested by the occurrence, in the same isolate or among different fungal samples, of isoforms with distinct isoelectric points. In the present study we aligned and compared with a consensus sequence the gp43 precursor genes of 17 P. brasiliensis isolates after sequencing two PCR products from each fungal sample. The genotypic types detected showed 1 to 4 or 14 to 15 informative substitution sites, preferentially localized between 578 and 1166 bp. Some nucleotide differences within individual isolates (noninformative sites) resulted in a second isoelectric point for the deduced protein. The most polymorphic sequences were also phylogenetically distant from the others and encoded basic gp43 isoforms. The three isolates in this group were from patients with chronic PCM, and their DNA restriction patterns were distinct in Southern blots. The nucleotides encoding the inner core of the murine T-cell-protective epitope of gp43 were conserved, offering hope for the development of a universal vaccine.

Partial chemical characterization of antigenic preparations of chromoblastomycosis agents

Antigenic preparations (saline, methylic, metabolic and exoantigens) of four agents of chromoblastomycosis, Fonsecaea pedrosoi, Phialophora verrucosa, Cladophialophora (Cladosporium) carrionii and Rhinocladiella aquaspersa were obtained. Partial chemical characterization of these antigenic preparations was obtained by determination of the levels of total lipids, protein, and carbohydrates, and identification of the main sterols and carbohydrates. Methylic antigens presented the highest lipid contents, whereas metabolic antigens showed the highest carbohydrate content. Total lipid, protein, and carbohydrate levels were in the range of 2.33 to 2.00 mg/ml, 0.04 to 0.02 mg/ml and 0.10 to 0.02 mg/ml, respectively, in the methylic antigens and in the range of 0. 53 to 0.18 mg/ml, 0.44 to 0.26 mg/ml, and 1.82 to 1.02 mg/ml, respectively, in saline antigens. Total lipid, protein, and carbohydrate contents were in the range of 0.55 to 0.20 mg/ml, 0.69 to 0.57 mg/ml and 10.73 to 5.93 mg/ml, respectively, in the metabolic antigens, and in the range of 0.55 to 0.15 mg/ml, 0.62 to 0.20 mg/ml and 3.55 to 0.42 mg/ml, respectively, in the exoantigens. Phospholipids were not detected in the preparations. Saline and metabolic antigens and exoantigens presented hexose and the methylic antigen revealed additional pentose units in their composition. The UV light absorption spectra of the sterols revealed squalene and an ergosterol fraction in the antigens. The characterization of these antigenic preparations may be useful for serological evaluation of patients of chromoblastomycosis.